Gold alloy for jewelry

ABSTRACT

TRACES OF ALUNINUM ARE ADDED TO GOLD ALLOYS OF A PREDETERMINED CARAT DESIGNATION TO PROVIDE A CLEAN AND BRIGHTER INVESTMENT CASTING FOR JEWELRY.

1974 D. R JORDAN 8,810,755

GOLD ALLOY FOR JEWELRY Filed Aug. 18. 1972 "United States Patent Offi 3,810,755 GOLD ALLOY FOR JEWELRY David R. Jordan, Bolton, Ontario, Canada, assignor to Johnson Matthey & Mallory Limited, Toronto, Ontario,

Canada Filed Aug. 18, 1972, Ser. No. 281,719 Int. Cl. C22c /00 US. Cl. 75-165 4 Claims ABSTRACT OF THE DISCLOSURE Traces of aluminum are added to gold alloys of a predetermined carat, designation to provide a clean and brighter investment casting for jewelry.

The present invention is concerned with the making of gold jewelry; and more particularly to the provision of a gold alloy from which jewelry may be made.

In the making of jewelry from precious metals such as gold alloys of a predetermined carat designation, the gold alloy is first formed into small pellets, shot, or grain and then each pellet is used to fabricate jewelry by an investment casting technique. The resulting castings from which jewelry, "such as rings, brooches, or charms are eventually made are usually very dirty or black as a result of the formation of a dark oxide during the casting process. These dirty or black castings are then subjected to a very rigorous cleaning process which usually involves pickling, grinding, and polishing to provide a piece of jewelry which is bright, clean, and smooth. Because of the black or dirty casting the cleaning process iadds materially to the final cost of the jewelry. Therefore the jewelry industry is constantly seeking ways and means of providing a more clean casting from which the jewelry may be fabricated.

The present invention is concerned with the art of making jewelry and has as one of its objects the provision of an investmentfcasting of a yellow gold alloy which is cleaner and brighter than heretofore known in the art.

Another object of the present invention is the provision of a yellow gold investment casting which is cleaner and therefore does not require as much cleaning in the making of jewelry as was previously required.

Still another object of the invention is the provision of an investment casting comprising a yellow gold alloy of a predetermined carat designation to which a trace of aluminum has been added.

Yet another object of the invention is the provision of a yellow gold grain for making jewelry comprising a gold alloy of a predetermined carat designation to which a trace of aluminum has been added.

These and other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 shows a plurality of yellow gold grains from which investment castings may be made;

FIG. 2 is a view showing a typical investment casting made from such grains; and a;

FIG. 3 is a photograph of various investment castings made from prior art gold alloys and gold alloys of the present invention.

Generally speaking, the object of the invention is accomplished by providing a yellow gold grain for making jewelry comprising a gold alloy of a predetermined carat designation and containing a trace of aluminum. The grain is used to make an investment casting which when completed will also comprise a yellow gold alloy of a predetermined carat designation containing a trace of aluminum.

Referring now to FIG. 1 there is shown grains comprised of a yellow gold alloy from which the jewelry may eventually be made. As is known in the art such alloys 3,810,755 Patented May 14, 1974 carry a carat designation such as 10K, 14K, and 18K, such designations meaning that there is a certain amount of gold with the balance being essentially copper, silver and sometimes zinc. Thus for example a designation of 10K means that there is approximately 41% gold. In general, the grains, sometimes referred to as shots or pellets, are made from a melt alloying process wherein a melt of the alloy is first provided, the grain then being formed by pouring the melt into a cooling medium such as water so that individual pellets are formed. This process is well known' in the jewelry art.

Referring to FIG. 2 there is shown an investment casting 12 which in general comprises a base number 14 to which are connected pieces of jewelry 16 through sprues 18. Although rings are illustrated as being the pieces of jewelry 16 it should be understood that various types of jewelry pieces such as brooches, charms and so forth may be formed. The investment castings are formed from the grain 10 of FIG. 1 by measuring out the prescribed amount of grain and then forming the casting by an investment casting technique well known in the jewelry art. Such investment casting technique has also been known as lost wax casting.

For the most part the investment casting, such as that shown in FIG. 2, have been very black or dirty due pri marily to the formation of dark oxides during the casting process. For example, with an 18K gold alloy, the resulting investment casting is known to be very black. In order to be useful in jewelry such casting had to go through several cleaning steps. For example, the casting had to be pickled and then ground and polished. Considerable improvement over these castings have been provided by the present invention.

In accordance with the present invention a trace of aluminum is added to the melt in the melt alloying process for providing the grain 10 of FIG. 1. When the gold alloy grain having a trace'of aluminum is used to provide the casting of FIG. 2, the resulting casting has been found to be yellow, bright and relatively smooth. With this casting it has been found that the pickling operation normally required to clean the casting is no longer needed, and all that is required is a relatively small amount of grinding and polishing. While not desiring to be so limited, it is felt that the aluminum reacts during the investment casting process to form alumina and so form a clear bright oxide at the surface of the casting.

In the practice of the invetion there must be sufficient aluminum added to the gold alloy to be effective. However, an excessive amount of aluminum would tend to cause some brittleness in the alloy. A desirable range for the amount of aluminum to be added appears to be from about .03% to 1% by weight of the alloy.

The photograph of FIG. 3 clearly shows the results of using a trace of aluminum in the gold alloy. The castings in column A arfeQthose prepared from alloys containing no aluminum while those of column B were prepared with an alloy using about .05 aluminum by weight of the alloy. The comparisons are made between 18K, 14K, and 10K gold alloys. Those castings in column B are clearly shown to be much lighter and brighter than those in column A.

What is claimed is:

1. A yellow gold grain for making jewelry comprising a gold alloy of a predetermined carat designation and containing aluminum in an amount of from about .03% to about 1% by weight of said alloy.

2. A yellow gold grain according to claim 1 wherein said gold alloy is of a class taken from a carat designation of 10, 14, and 18 carats.

3. An investment casting comprising a yellow gold alloy of a predetermined carat designation and containing alu- 3 4 minum in anamount of from about .03% to about 1% by FOREIGN PATENTS welght Of Sand 633,310 12/1949 Great Britain 75-165 4. An investment casting according to claim 3 wherein said gold alloy is of a class taken from a carat designation L DEWAYNE RUTLEDGE, Primary Examiner 10.14, d18 0 an Cara S 5 E. L. WEISE, Assistant Examiner References Cited U S Al XR UNITED STATES PATENTS C, 134 N 3,613,209 10/1971 Piguerez 75-465 X 

